Field of Invention
The present disclosure relates to a voltage adjusting technology. More particularly, the present disclosure relates to a voltage-adjusting device and a method in a power conversion system.
Description of Related Art
With the requirements of energy conservation and carbon reduction and green environmental protection, variable frequency speed regulation motors have broader and broader applications in industrial systems. In recent years, the demand for high-voltage variable frequency systems has significantly increased, and the performance requirements has become more and more stringent. In a high-voltage variable frequency system, the higher the voltage of a direct current (DC) bus that connects a rectifier and a inverter is, the higher the voltage that switches in the rectifier and the inverter need to sustain and consequently the switches have an increased failure rate. In addition, a lifetime of a DC bus capacitor tends to be shortened. In addition to that, when the motor sustains a higher voltage, the motor winding insulation devices will withstand a bigger challenge. In order to improve the system reliability, the DC bus voltage needs to be ensured to operate at as low a level as possible.